In the construction of many concrete members and particularly floor slabs and slab walls it has been found to be particularly advantageous to use a prestressed concrete construction. Tupicaly, a plurality of tendons and tendon anchorages are placed within the concrete forms and the concrete is then poured with the tendon and anchorage being cast-in-place. The forms are then removed and the tendons are tensioned. It also has been found to be desirable in many applications to have the tenson anchorage located in a recess in the end of the concrete member, which recess is subsequently grouted so that the anchorage is completely contained within the finished prestressed concrete member. When this type of construction is used, the tendon anchorage must be located and positioned in fixed spaced relation to the concrete form by means of apparatus which, after casting of the concrete member, afford access to the anchorage for tensioning of the tendon.
Several anchorages have been previously employed in order to provide an anchorage construction which can be cast-in-place at a position interiorly of the ends of the concrete member. Two such anchorage constructions are illustrated in U.S. Pat. Nos. 3,293,811 and 3,399,434. Another approach has been to provide a unitary anchorage member which is formed with screw threads or a bayonet-type socket on the side of the anchorage facing the form. A mounting member is then screwed into the front of the anchorage and extends therefrom to and through the form.
Prior cast-in-place anchorage systems have been found to have several disadvantages. Primary among these disadvantages is the inflexibility of the system for mounting the anchorage in spaced relation to the concrete form. As will be readily understood, the prestressing reqirements of various concrete members may differ considerably. For example, the depth to which a cast-in-place anchorage must be placed in the concrete member may under different construction codes vary from state to state or locality to locality. Similarly, tensioning forces may require various sizes or shapes of bearing surfaces in order to properly distribute the axial loading of the tendon or tendons. Moreover, close grouping of tendons may result in special bearing plate requirements. Still further, special wedge containing anchor members may be required for given stress conditions. Thus, prior tendon anchorages hve lacked an interchangeability or flexibility of the elements in the systems which would allow the structural engineer maximum flexiblity of design.
Accordingly, it is an object of the concrete prestressing tendon anchorage of the present invention to provide an improved anchorage construction and method of anchorage support which affords greater flexiblity in meeting design criteria by means of allowing easy interchangeability of the parts while maintaining the characteristic of being rapidly mountable on the concrete form for casting of the concrete member.
It is another object of the present invention to provide a tendon anchorage wherein the parts of the anchorage can be readily and easily formed, stored and shipped.
It is still another object of the tendon anchorage of the present invention to provide an anchorage construction which can be conveniently and easily adjusted under field conditions and minimizes the exposure of the anchorage to damage and corrosion in the field.
Still another object of the tendon anchorage of the present invention is to provide an anchorage construction wherein a multiplity of side-by-side tendons can be conveniently and easily secured.